In this paper， the welding process of helium arc bottoming + argon arc filling and covering was used to conduct TIG welding experiment on 15 mm thick plate of 2219-T87 aluminum alloy to study its weld formation，microstructure and mechanical properties. The results show that this process has good weld appearance， no visible welding defects， and good porosity inhibition effect. The average tensile strength of the joint is 278.22 MPa， the average elongation after fracture is 3.89%， and the average strength coefficient of the joint reaches 58.94%. The overall performance of the joint hardness is the lowest in the center of the weld. From the center of the weld to the base material， the hardness first increases， then decreases locally， and then increases； and the hardness of the filler layer in the center of the weld is higher than that of the bottom layer and the cover layer. The microstructure of the fusion zone is columnar dendrite and cellular dendrite， and grows perpendicular to the fusion line. Equiaxed fine grain bands appear on both sides of the fusion zone. There are many tearing edges and dimples on the cross section of the welded joint， and micropores and second phase particles are found locally. The fracture mechanism of the welded joint is typical ductile fracture.